1. Field of the Invention
The present invention relates to a suction recovery device for discharging liquid from a pump after it was sucked, and a recording system such as a copying machine, facsimile, computer, word processor and combination thereof, having such a recovery device, and more particularly, it relates to an ink jet recording system wherein the suction recovery device of the above-mentioned type is applied to an ink receiving member such as a cap for receiving waste ink from a recording head.
2. Related Background Art
In the past, in an ink recording system wherein an ink image is recorded on a recording medium such as a cloth, paper, OHP sheet and the like (referred to as "recording sheet" or merely as "sheet" hereinafter), a recording head having an array of minute or small discharge openings has been used. Therefore, when bubbles and/or dirt are entered into the discharge opening or openings or when the viscosity of ink is increased due to the vaporization of solvent in the ink, which lead to the poor ink discharge or poor recording, or before such a poor condition occurs, a treatment for removing the factors leading to the poor ink discharge (discharge recovery treatment) has been adopted.
Normally, a preliminary discharge operation for discharging the ink from the discharge openings (for example, toward a cap or ink absorbing sheet or sponge) without recording an image on a sheet or a suction recovery operation effected by a pump communicated with a cap to generate a suction force in the cap has been used as the discharge recovery treatment.
On the other hand, within the recording system, there is disposed a waste ink tank for collecting waste ink produced by the discharge recovery treatment. Further, an idle suction operation for sucking the ink together with air by activating the pump while communicating the cap with the atmosphere is also effected in order to direct the waste ink contained in the discharge recovery device including the cap, pump and a waste ink tube connecting them to each other to the waste ink tank. This idle suction operation is very effective to prevent the residual waste ink from being solidified or from leaking out of the cap if the waste ink produced by the discharge recovery treatment is left in the discharge recovery device.
Further, such a pump has been used not only to suck the waste ink but also to discharge normal liquids to predetermined positions in various applications.
However, the idle discharge operation was generally effected at a high speed to prevent the delay in the discharge recovery treatment, with the result that the liquid sucked by the pump tended to flow backwardly or reversely. This tendency is particularly noticeable when the pump has been used for a long time.
Similarly, even when the idle suction operation is effected by a discharge recovery mechanism wherein the interior arrangement within a cylinder thereof is simplified by omitting a normal check valve mechanism, the above-mentioned back flow frequently occurs. In addition since the suction recovery mechanism requires a large installation space within the recording system, in order to make the recording system small-sized, it is needed to make the suction recovery device itself small-sized. However, the smaller the recovery device the more the above-mentioned back flow problem is serious. Thus, it has been recognized that it was important to solve this problem.
As mentioned, if the ink once sucked flows reversely, there arises a problem that the ink is scattered in bubble forms with air from the cap to adhere to a recording head opposed to the cap. The ink adhered to the recording head adversely affects an ink discharge condition. That is to say, the ink adhered to the discharge openings and therearound of the recording head pulls ink droplets discharged from the discharge openings, thus deviating the ink droplets from their normal paths.
Further, although a wiping operation is effected to remove the excessive ink droplets on the recording head during the discharge recovery treatment, if an amount of ink adhered to the recording head is great, a wiping blade is liable to become dirty easily, with the result that, when a large number of prints are continuously produced, the wiping ability is reduced, thus worsening the recording quality. Although it is considered that a special valve mechanism is provided for preventing the back flow of the bubble-form ink, there arises a drawback that the system is bulky and the cost thereof is increased. Further, when the ink flows reversely, the amount of the residual waste ink in the system increases. Under this condition, if the recording system is left for a long time, the waste ink will be solidified, thus resulting in the malfunction of the recovery device.